Abdominal Aortic Aneurysm

Presents as a triad of:

Abdominal or Back Pain of sudden onset

Collapse or Light-headedness

Hypotension

• An abnormal blood-filled dilatation of a blood vessel (esp. in an artery resulting from disease of the vessel wall)
• An abdominal catastrophe ( 30% misdiagnosed initially)
• Abdominal aorta begins at the level of the aortic hiatus of the diaphragm at T12
• Surface anatomy = Xiphoid sternum (dilated aorta palpable above the umbilicus)
• The dilatation is part of a atherosclerotic process
• An aneurysm is defined as a focal increase in the diameter (normal 2cm) of a vessel to greater than 50% of normal; anything less is considered arteriomegaly

Risk factors

• Male
• Age (biological age)
• Smoking
• Hypertension
• FHx
• Hypercholesterolaemia
• Peripheral Vascular Disease
• Diabetes in protective against AAA

Presentation

Sudden Pain

• Back / Abdomen / Flank
• Inguinal / Testicular

Collapse (Light-headedness)

Aortocaval fistula

• High output cardiac failure
• Pulmonary oedema (flash)
• Leg congestion and swelling

Examination

• Unwell
• Hypotensive
• Diaphoretic
• SOB
• Abdo. mass (pulsatile & expansile)

Initial Mx

• Surgical On-Call when Dx suspected
• Aim for Stable hypotension in resusc

Investigations:

• Group Xmatch x6
• FBC, U&E, Creat, Coag
• ECG (Hardman Criteria)/AMI
• Urinalysis - UOB negative
• U/S Aorta (bedside)
• CT Abdomen - if stable

Differential Diagnosis:

• Perforated Viscus
• Aortic Dissection
• Myocardial Infarction
• Ureteric Colic
• Neurogenic Back Pain
• Mechanical Back Pain
• Discitis

Surgical Prognosis Determined by:

Hardman Criteria:

Age > 76	+3 = 100% Mortality +2 = 72% Mortality +1 = 37% Mortality
Hb <9.0 g/dl
Creat >190mmol/l
Hx of LOC
Ischaemia on ECG

Additional Management:

• Urinalysis - Qualitative Microscopic Haematuria
• Urinary Catheter - Monitor Urinary Output
• ABG - Acid/Base Status, Lactic Acid (bowel?)
• Erect CXR - Free Air?
• AXR not useful but may show loss psoas shadow
  • Approximately 90% (of AAA) are infrarenal
  • The average increase is 2 mm/yr diameter
  • Usually not repaired until they exceed 4-5 cm
  • Risk of rupture within 5 years is 25% at 5 cm diameter
  • AAA > 5 cm have a 3% risk of rupture over 10 years